The present invention relates to a programmable pulse generator for generating a pulse in response to a trigger signal wherein the timing of the leading and trailing edges of the pulse are programmable.
A one use for a pulse generator is as a strobe pulse generator for a digital word generation system which is used to simulate digital systems such as microcomputer systems. In this instance, the time relationship between the strobe pulse and the digital word pattern from the word generation system must be determined in accordance with the construction of the digital system under test. If the time relationship between the word pattern and the strobe pulse is not proper for the digital system, it cannot acquire the word pattern. So that the word generation system is applicable to many kinds of digital systems, a programmable pulse generator is necessary to generate a strobe pulse, the leading and trailing edges of which are programmable.
Since the word generation system generates the word pattern in accordance with a clock signal, such clock signal may be used as a trigger signal to generate the strobe pulse. However, the clock signal cannot determine the timing of the leading and trailing edges of the strobe pulse, because the clock signal occurs on every cycle of the word pattern and is not synchronized with the leading and trailing edges of the strobe pulse. For determining the time occurrence of the leading and trailing edges of the strobe pulse, a digital delay circuit and/or a monostable multivibrator may be used, and such circuits may be triggered by the clock signal from the word generation system. However, digital delay circuits are complex and expensive, and two such digital delay circuits are necessary to determine both the leading and trailing edges of the strobe pulse. Since the monostable multivibrator uses charge and discharge characteristics of a time constant circuit, the pulse width from the multivibrator varies with the power supply voltage and it is difficult to control the pulse width exactly. Moreover, a plurality of conventional pulse generators are necessary to generate multi-phase strobe pulses.